Comment by kkfx
12 hours ago
There's actually no substantial difference: it's the very concept of a mere filesystem that's obsolete. What's needed to manage your data is:
- Lightweight/instant/accessible and transmittable (at block-level) snapshots, not just logical access
- Integrated management of the underlying hardware, meaning support for various RAID types and dynamic volumes
- Simplicity of management
ZFS offers this, btrfs doesn't (even with LUKS + LVM, nor stratis); it has cumbersome snapshots, not transmittable at the block level, and has embryonic RAID support that's definitely not simple or useful in practice. Ext? Doesn't even have snapshots nor embryonic RAID nor dynamic volumes.
Let me give a simple example: I have a home server and 2 desktops. The home server acts as a backup for the desktops (and more) and is itself backed up primarily locally on cold storage. A deployment like this with NixOS, via org-mode, on a ZFS root is something that can be done at the home level. ZnapZend sends daily snapshots to the home server, which is backed up manually every day simply by physically connecting the cold storage and disconnecting it when it's done (script). That's the foundation.
What happens if I accidentally deleted a file I want back? Well, locally I recover it on the fly by going to $volRoot/.zfs/snapshots/... I can even diff them with Meld if needed. What happens if the single NVMe in the laptop dies?
- I physically change the NVMe on my desk, connect and boot the laptop with a live system on a USB NVMe that boots with sshd active, a known user with authorized keys saved (creating it with NixOS is one config and one command; I update it monthly on the home server, but everything needed is anyway in an org-mode file)
- From there, via ssh from the desktop, with one command (script) I create an empty pool and have mbuffer+zfs recv listening; the server via mbuffer+zfs send, send the latest snapshots of everything (data and OS)
- When it's done, chroot, rebuild the OS to update the bootloader, reboot by disconnecting the USB NVMe, and I'm operational as before
- what if one of mirrored two NVMEs of my desktop die? I change the faulted and simply wait for resilvering.
Human restore time: ~5 minutes. Machine time: ~40 minutes. EVERYTHING is exactly as before the disk failed; I have nothing to do manually. Same for every other machine in my infra. Cost of all this? Maintaining some org-mode notes with the Nix code inside + machine time for automated ISO creation, backup incremental updates etc.
Doing this with mainstream distros or legacy filesystems? Unfeasible. Just the mere logical backup without snapshots or via LVM snaps takes a huge amount of time; backing up the OS becomes unthinkable, and so on. That's the point.
Most people have never built an infra like this; they've spent HOURS working in the shell to build their fragile home infra, when something breaks they spend hours manually fixing it. They think this is normal because they don't know anything else to compare. They think a setup like the one described is beyond home reach, but it's not. That's why classic filesystems, from ext to xfs (which does have snapshots) passing through reiserfs, btrfs, bcachefs and so on, make no sense in 2026 and not even in 2016.
They are software written even in recent times, but born and stuck in a past era.
Or you just fully embrace the thin client life and offload everything to the server. pxe boot with remotely mounted filesystems. local hard drives? who needs those?
And the server is handled how? We're always there: complexity can be managed or hidden.
Why do you think some people asked SUN to un-free ZFS back in the day? Because unlike most, they understood its potential. Why do you think PC components today, graphics cards first, then RAM, and NVMe drives after that, cost so much? Because those who understand realize that today, a GNU/Linux homeserver and desktop are ready for the masses, and it's only a matter of time before a umbrel.com, start9.com, or even frigghome.ai succeeds and sweeps away an increasingly banning and therefore unreliable and expensive cloud providers. Most still haven't grasped this, but those who live above the masses have.
Why are snaps, flatpaks, docker etc are pushed so hard even though they have insane attack surfaces, minimal control over your own infrastructure, and are a huge waste of resources? Because they allow selling support to people who don't know. With NixOS or Guix, you only sell a text config. It's not the same business model, and after a while, with an LLM, people learn to do it themselves.
The scenarios you mentioned are indeed nice use cases of ZFS, but other tools can do this too.
I can make snapshots and recover files with SnapRAID or Kopia. In the case of a laptop system drive failure, I have scripts to quickly setup a new system, and restore data from backups. Sure, the new system won't be a bit-for-bit replica of the old one, and I'll have to manually tinker to get everything back in order, but these scenarios are so uncommon that I'm fine with this taking a bit more time and effort. I'd rather have that over relying on a complex filesystem whose performance degrades over time, and is difficult to work with and understand.
You speak about ZFS as if it's a silver bullet, and everything else is inferior. The reality is that every technical decision has tradeoffs, and the right solution will depend on which tradeoffs make the most sense for any given situation.
How often do you test your OS replication script? I used to do that too, and every time there was always something broken, outdated, or needing modification, often right when I desperately needed a restore because I was about to leave on a business trip and had a flight to catch with a broken laptop disk.
How much time do you spend setting up a desktop and maintaining it with mdraid+LUKS+LVM+your choice of filesystem, replacing a disk and doing the resilvering, or making backups with SnapRAID/Kopia etc? Again, I used to do that. I stopped after finding better solutions, also because I always had issues during restores, maybe small ones, but they were there, and when it's not a test but a real restore, the last thing you want is problems.
Have you actually tested your backup by doing a sudden, unplanned restore without thinking about it for three days before? Do you do it at least once a year to make sure everything works, or do you just hope that since computers rarely fail and restores take a long time, everything will work when you need it? When I did things like you and others I know who still do it, practically no one ever tested their restore, and the recovery script was always one distro major release behind. You had to modify it every few releases when doing a fresh install. In the meantime, it's "hope everything goes well or spend a whole day scrambling to fix things."
Maybe a student is okay with that risk and enjoys fixing things, but generally, it's definitely not best practice and that's why most are on someone else's computer, called the cloud, as protection from their IT choices...
> How often do you test your OS replication script?
Not often. It's mostly outdated, and I spend a lot of time bringing it up to date when I have to rely on it.
BUT I can easily understand what it does, and the tools it uses. In practice I use it rarely, so spending a few hours a year updating it is not a huge problem. I don't have the sense of urgency you describe, and when things do fail, it's an extraordinary event where everything else can wait for me to be productive again. I'm not running a critical business, these are my personal machines. Besides, I have plenty of spare machines I can use while one is out of service.
This is the tradeoff I have decided to make, which works for me. I'm sure that using ZFS and a reproducible system has its benefits, and I'm trying to adopt better practices at my own pace, but all of those have significant drawbacks as well.
> Have you actually tested your backup by doing a sudden, unplanned restore without thinking about it for three days before?
No, but again, I'm not running a critical business. Things can wait. I would argue that even in most corporate environments the obsession over HA comes at the expense of operational complexity, which has a greater negative impact than using boring tools and technology. Few companies need Kubernetes clusters and IaaC tools, and even fewer people need ZFS and NixOS for personal use. It would be great if these benefits were accessible to more people and had less drawbacks, but the technology is not there yet. You shouldn't gloss over these issues because they're not issues for you.